Torque detector with reflector for electric power steering system

ABSTRACT

The present invention relates to a steering torque detecting apparatus of an electric power steering system which is capable of assisting a steering operation by accurately detecting a steering torque b providing a light incident groove having a reflections surface. In a steering system which includes an input shaft connected with a steering handle, an output shaft which is connected with vehicle wheels, an elastic member which connects the input shaft and output shaft to be rotatable in different directions at a certain angle, and a steering torque detector which is installed between the input shaft and the output shaft for thereby detecting a steering torque, there is provided a steering torque detector of a steering system which includes left and right reflections surfaces formed in one of the input shaft and output shaft, a light emitting element which is installed in a shaft corresponding to a shaft in which the reflection surface is formed, and left and right light receiving elements which are installed in left and right sides of the light emitting element and receive light of the light emitting element in accordance with a relative rotation of the input shaft and output haft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a torque detector with a reflector foran electric power steering system, and in particular to a torquedetector with a reflector for an electric power steering system which iscapable of decreasing the number of wires and elements, implementing asimple construction and enhancing a reliability and durability byproviding a light incident groove having a reflection surface forthereby accurately detecting a steering torque.

2. Description of the Background Art

When rotating a steering handle when a vehicle runs or stops, a wheelcontacting with a ground surface is moved in a certain directioncorresponding thereto. Since a certain friction force is applied betweena wheel and a ground surface, a large force is required for operating asteering handle. The steering torque detector of an electric powersteering system is an apparatus for enhancing a steering convenience ofa vehicle by measuring a rotations state of a steering handle andproviding an assistant steering force to a steering shaft by an electricpower motor.

In the electric power steering system, an input shaft connected with thesteering handle and an output shaft connected with the wheels areconnected by a torsion bar. The input shaft and output shaft areconnected by the torsion bar in such a manner that the same are rotatedin different directions, respectively, so that a steering torqueinputted through the steering handle and input shaft are transferred tothe output shaft by the torsion bar. When operating the steering handle,the torsion bar is deformed, so that a certain variation of a certainangle occurs between the input shaft and the output shaft. A steeringtorque detector is installed between the input shaft and the outputshaft. The motor connected with the output shaft is controlled by asignal generated by the detector for thereby generating an assistanttorque and supporting the steering operation.

The steering torque detector is classified into a contact type and anon-contact type based on the truth that whether the input shaftconnected with the steering handle contacts with the steering shaft. Inthe contact type, there is a method in which a potentiometer or magnetictransformer. In the above contact type steering torque detector, thevolume and weight are large, and a detection accuracy is bad, and asignal process is complicated. Since the steering shaft and the detectorare contacted, an inherent torque characteristic of the steering shaftis affected.

In the non-contact type steering torque detector, there is not anycontact with respect to the input shaft, and a mechanical constructionis not complicated. The construction is simple for thereby decreasing afabrication cost. It is possible to accurately detect the steeringtorque. Therefore, the non-contact type steering torque detector islargely used and substitutes the contact type steering torque detector.

In the Korean patent laid-open No. 99-276609-11, the steering torquedetector of the electric power steering system has a light emittingelement and a light receiving element in the input shaft and outputshaft for thereby measuring a distorted angle between the output andinput shafts.

However, the above conventional steering torque detector has acomplicated construction, and it is difficult to process each element.It is not easy to install a light emitting element, light receivingelement and wire in the input and output shafts. Therefore, thefabrication cost is increased, and the durability has erroneousproblems.

In the steering torque detector of the Korean patent laid-open No.97-040971, a slide is installed in a torsion bar to be moved upwardlyand downwardly. A reflection plate is vertically extended in the slide.A light emitting element and light receiving element are installed inthe upper and lower portions of the reflection plate. Therefore, thesteering torque is detected using a reflection degree of light which ischanged based on the upward and downward movements of the slide. In theabove conventional steering torque detector, in order to upwardly anddownwardly move the slide based on the rotation of the torsion bar,various elements should be provided in the torsion bar for therebycomplicating the construction. In addition, in this case, the processand assembling are difficult.

In order to overcome the above problems, there is provided a steeringtorque detector. In the above conventional steering torque detector, alight emitting element is installed in one shaft between the input andoutput shafts, and a light receiving elements is installed in the othershaft. In an initial position in which the steering handle is notoperated, the light emitting element and the light receiving element arenot overlapped, and when the steering handle is operated, as the inputshaft and output shaft are relatively rotated, so that the lightemitting element and the light receiving element are partiallyoverlapped. When the light receiving element is partially overlappedwith the light emitting element, an electric signal is outputted inproportion to the degree of opening formed in such a manner that the twoelements are overlapped, for thereby detecting the steering torque. Inthe thusly constructed conventional steering torque detector, theconstruction is simple. The wires should be separately connected in thelight emitting element and light receiving element for thereby causing adifficult installation. Since there is a region in which the outputsignal of the light receiving element is sharply changed due to thedegree of opening due to the optical characteristic of the lightemitting element, it is not adaptable to use as a control signal.

FIG. 7 is a graph of an output electric signal of a light receivingelement of the steering torque detector in the conventional art. Theaxis X represents an area in which the light receiving element and thereflection surface are overlapped, and the axis Y represents an outputelectric signal of the light receiving device.

As shown in FIG. 7, since the light emitting element has an intensitywhich is increased in the direction of its center portion, it is not inproportion to the degree of opening in which the light receiving elementand the output electric signal are overlapped and is sharply changed atthe moment that the light receiving element becomes close to the lightemitting element. Therefore, the control signal inputted into the motormay be sharply changed, so that it is impossible to implement a smoothsteering operation in the conventional art.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide atorque detector with a reflector for an electric power steering systemwhich is capable of decreasing the numbers of wires and parts in anelectric power steering system and implementing a simple construction.

It is another object of the present invention to provide a torquedetector with a reflector for an electric power steering system which iscapable of accurately detecting a steering torque by installing asteering torque detector having an improved reliability and durability.

In order to achieve the above objects, in a steering system whichincludes an input shaft connected with a steering handle, an outputshaft which is connected with vehicle wheels, an elastic member whichconnects the input shaft and output shaft to be rotatable in differentdirections at a certain angle, and a steering torque detector which isinstalled between the input shaft and the output shaft for therebydetecting a steering torque, there is provided a torque detector with areflector for an electric power steering system which includes left andright reflections surfaces formed in one of the input shaft and outputshaft, a light emitting element which is installed in a shaftcorresponding to a shaft in which the reflection surface is formed, andleft and right light receiving elements which are installed in left andright sides of the light emitting element and receive light of the lightemitting element in accordance with a relative rotation of the inputshaft and output haft.

In the present invention, the left and right reflection surfaces areformed in the upper surfaces of left and right light incident groovesformed in an end portion of an input shaft flange integrally formed inthe input shaft, and the light emitting element and left and right lightreceiving elements are installed an output shaft flange integrallyformed in the output shaft in correspondence to the input shaft flange.

In addition, the left and right light incident grooves and left andright reflection surfaces are formed in such a manner that through hoesare formed in the input shaft flange, and a reflection plate isinstalled thereon.

A protrusion is formed in one of the output shaft flange and the inputshaft flange, and a guide groove is formed in other shaft flangecorresponding to the shaft in which the protrusion is formed, and theprotrusion is inserted into the guide grove for thereby limiting arelative rotation angle of the input shaft.

The light emitting element induces a resistance which is in reverseproportion to the intensity of incident light.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become better understood with reference tothe accompanying drawings which are given only by way of illustrationand thus are not limitative of the present invention, wherein;

FIG. 1 is a schematic view illustrating an electric power steeringsystem with a steering torque detector according to an embodiment of thepresent invention;

FIG. 2 is a vertical cross sectional view illustrating a steering torquedetector according to an embodiment of the present invention;

FIG. 3 is a partial perspective view illustrating a steering torquedetector according to an embodiment of the present invention;

FIG. 4 is a partial cross sectional view illustrating a steering torquedetector according to an embodiment of the present invention;

FIG. 5 is a partial plan view illustrating an operation state of asteering torque detector according to an embodiment of the presentinvention;

FIG. 6 is a graph of an output electric signal of a steering torquedetector according to an embodiment of the present invention; and

FIG. 7 is a graph of an output electric signal of a photo detector of asteering torque detector in the conventional art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The construction and operation of a steering torque detector of anelectric power steering system according to the present invention willbe described through the preferred embodiments of the present inventionwith reference to the accompanying drawings.

FIG. 1 is a schematic view illustrating an electric power steeringsystem with a steering torque detector according to an embodiment of thepresent invention.

As shown therein, in the electric power steering system, the wheels (notshown) are steered based on a steering shaft 10 which is integrallyrotated with a steering handle 1 and an operation of the steering handle1 in which a steering link 60 in which the wheels are installed at bothends of the same, is connected with the steering shaft 10.

The steering shaft 10 is formed of an input shaft 11 and an output shaft12. The input shaft 11 is rotated by the steering handle 1 for therebytransferring a rotational force, and the output shaft 12 is connectedwith the input shaft 11 by a torsion bar 13 which is formed of anelectric member for thereby being rotated at a certain angle withrespect to the input shaft 11.

A steering torque detector 2 is installed in the input shaft 11 and theoutput shaft 12, respectively, and a motor 61 is connected through adecelerator 62 on the output shaft 12 for thereby generating anassistant steering torque based on a detection signal from the steeringtorque detector 2. The motor 61 may be connected to the steering link 60through the decelerator 62.

FIG. 2 is a vertical cross sectional view illustrating a steering torquedetector according to an embodiment of the present invention, and FIG. 3is a partial perspective view illustrating a steering torque detectoraccording to an embodiment of the present invention.

As shown therein, the steering torque detector 2 according to thepresent invention includes left and right reflection plates 22 and 23installed in the input shaft 11, respectively, a light emitting element31 installed in the output shaft 12, and left and right light receivingelements 32 and 33.

The input shaft 11 and the output shaft 12 are connected by the torsionbar 13 which is an elastic member. One end of the torsion bar 13 isconnected with the steering handle 1 and is inserted into a centerportion of the input shaft 11 and is connected by a pin 14. The otherend of the same is connected with the output shaft 12 by a pin 14. Whena steering torque is transferred to the input shaft 11 based on anoperation of the steering handle 1, a certain torsion force occurs inthe torsion bar 13, so that the input shaft 11 and the output shaft 12are relatively rotated.

An output shaft flange 30 is extended in an outer portion of the upperportion of the output shaft 12 corresponding to the input shaft 11, anda light emitting element 31 is inserted and installed in an end portionof one side of the output shaft flange 30, and the left and right lightreceiving elements 32 and 33 are installed in left and right portions ofthe light emitting element 31.

An input shaft flange 20 is extended in an outer portion of the lowerportion of the input shaft 11 corresponding to the output haft 12. Twothrough holes are formed in the end portion of one side of the inputshaft flange 20 for thereby forming left and right incident grooves 21 aand 21 b for thereby being corresponded to the left and right lightreceiving elements 32 and 33. The left and right reflection plates 22and 23 are attached to the upper surfaces of the through holes forthereby operating as a reflection surface capable of reflecting light ofthe light emitting element 31.

When forming the reflection surface and the left and right incidentgrooves 21 a and 21 b in the input shaft flange 20, there may be variousmethods. In one method, a groove (not shown) is processed after anadditional reflection plate is not attached, the inner upper surface ispolished for thereby integrally forming the reflection surface (notshown).

The left and right light receiving elements 32 and 33 and the lightemitting element 31 are connected with a wire portion 34 installed inthe output shaft 12 for thereby externally receiving a power andexternally outputting a signal. The left and right light receivingelements 32 and 33 are connected with an amplifier 63 of a power circuitwhich supplies power to the motor 61 through the wire portion 34 andinduces a resistance which is in reverse proportion to the intensity ofinputted light with respect to the power applied to the amplifier 63.Since only the left and right reflection plates 22 and 23 are installedin the input shaft 11, it is not needed to connect an additional wire.

A circumferential direction guide groove 24 having a certain length isformed in an outer portion of the rear end of the input shaft flange 20,and a protrusion 35 inserted into the guide groove 24 is formed in theoutput shaft flange 30. The input shaft 11 and the output shaft 12 arerelatively rotated in a range in which the protrusion 35 is moved alongthe guide groove 24, and when the protrusion 35 is contacted with bothends of the guide groove 24, the input shaft 11 and the output shaft 12do not rotated any more.

FIG. 4 is a partial cross sectional view illustrating a steering torquedetector according to an embodiment of the present invention, of whichFIG. 4A is a cross sectional view of an input shaft flange, and FIG. 4Bis a cross sectional view of an output shaft flange.

As shown in FIG. 4B, the left and right light receiving elements 32 and33 are installed to have a certain identical angle θ from the center ofthe light emitting element 31 with respect to a center of the outputshaft 12, and the protrusion 35 is opposite to the light emittingelement 31 in such a manner that the center of the same is positioned ina diagonal line passing through the center of the light emitting element31.

As shown in FIG. 4A, left and right light incident grooves 21 a and 21 bare formed in the input shaft flange 20, and left and right reflectionplates 22 and 23 are installed in the upper surface of the same. When acertain variation occurs in the input shaft 11 and the output shaft 12,the light of the light emitting element 31 passes through the lightincident grooves 21 a and 21 b and is reflected by the reflectionsurfaces 22 and 23 and are made incident into the left and right lightreceiving elements 32 and 33. The left and right reflection plates 22and 23 and the left and right light incident grooves 21 a and 21 b areformed in an elliptical shape. In this state, the left and rightreflection plates 22 and 23 and the left and right light incidentgrooves 21 a and 21 b have a certain length in the circumferentialdirection so that the left reflection plate 22 and the left lightincident groove 21 a may be overlapped with the light emitting element31 and the left light receiving element 32 at one time, and the rightreflection plate 23 and the right light incident groove 21 b areoverlapped with the light emitting element 31 and the right lightreceiving element 33. The left and right reflection plates 22 and 23 aredistanced in the left and right directions with respect to the lightemitting element 31 so that one end of each left and right reflectionplate 22 and 23 is overlapped with only the left and right lightreceiving elements 32 and 33 and is not overlapped with the lightemitting element 31 in a state that the input shaft 11 and the outputshaft 12 are not rotated relatively.

The protrusion 35 is inserted into the guide groove 24 and is moved inthe left and right directions based on a relative rotation of the inputshaft 11 and the output shaft 12, and the left and right movements arelimited by the length of the guide groove 24. The length of the guidegroove 24 is determined in such a manner that the input shaft 11 and theoutput shaft 12 are rotated at an angle range of θ.

When constructing a limit in the relative rotation angle of the inputshaft 11 and the output shaft 12, various constructions may be adaptedin addition to the construction that the protrusion 35 and the guidegroove 24 are formed in the above manner.

FIG. 5 is a partial plan view illustrating an operation state of asteering torque detector according to an embodiment of the presentinvention, of which FIG. 5A is a view illustrating a neutral state inwhich the input shaft 11 and the output shaft 12 are not relativelyrotated, FIG. 5B is a view illustrating a left steering state in whichthe steering handle 1 is rotated in the left direction, and FIG. 5C is aright steering state in which the steering handle 1 is rotate din theright direction.

As shown in FIG. 5 a, in a state that the steering handle 1 is notoperated, the light of the light emitting element 31 is not inputtedinto the left and right light receiving elements 32 and 33, the left andright light emitting elements 32 and 33 have a unlimited resistance.Therefore, the power of the amplifier 63 is disconnected, and the motor61 is not driven.

As shown in FIG. 5B, when the steering handle 1 is steered in the leftdirection, the input shaft 11 and the output shaft 12 are relativelyrotated, and the right reflection surface 23 is partially overlappedwith the light emitting element 31. The light from the light emittingelement 31 is reflected by the reflection surface 23 and is madeincident into the right light receiving element 33. The right lightreceiving element 33 has a resistance which is in reverse proportion tothe area overlapped with the reflection surface 22 with respect to thepower of the amplifier 63. Therefore, the power which is in proportionto the rotation angle of the input shaft 11 is inputted into theamplifier 63, so that the motor 61 outputs an assistant steering torqueof a certain size corresponding to the rotational angle of the inputshaft 11.

As shown in FIG. 5C, the steering handle 1 is steered in the rightdirection, and the left reflection surface 22 is partially overlappedwith the light emitting element 31, and the light of the light emittingelement 31 is inputted into the left light receiving element 32 forthereby obtaining a resistance which is in reverse proportion to theintensity of incident light.

Even when the steering handle 1 is rotated in the left direction orright direction by a few numbers, the movement of the protrusion 35 islimited by both ends of the guide groove 24, and the relative rotationof the input shaft 11 and the output shaft 12 is limited. Therefore,since the input shaft 11 is continuously relatively rotated with respectto the output shaft 12, it is possible to prevent the right reflectionsurface 23 from detecting the light and the right light receivingelement 33 from detecting the light of the left reflection surface 22,for thereby preventing an error detection.

FIG. 6 is a graph of an output electric signal of a steering torquedetector according to an embodiment of the present invention, in whichthe axis X represents an area in which the left and right lightreceiving elements 32 and 33 are overlapped with the left and rightreflection plates 22 and 23, and the axis Y represents a currentinputted into the amplifier 63 by a varying resistance of the lightreceiving element. As shown therein, since an electric signal inputtedinto the amplifier 63 by the steering torque detector 2 is in proportionto the area in which the left and right light receiving elements 32 and33 are overlapped with the left and right reflection plates 22 and 23,the signal may be well adapted to be used as a control signal forcontrolling the motor 61. Therefore, it is possible to more accuratelydetect the steering torque.

As described above, in the steering torque detector of an electric powersteering system according to the present invention, it is possible toassist a steering operation by accurately detecting the steering torqueby providing a light incident groove having a reflection surface. It isnot needed to connect a wire to the input shaft. The numbers of thewires and parts are decreased for thereby implementing a simpleconstruction. An installation work is easy. The wires are notdisconnected by the relative rotation of the input shaft and the outputshaft for thereby enhancing a durability and reliability.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described examples are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the meets and bounds of theclaims, or equivalences of such meets and bounds are therefore intendedto be embraced by the appended claims.

1. In a steering system which includes an input shaft connected with asteering handle, an output shaft which is connected with vehicle wheels,an elastic member which connects the input shaft and output shaft to berotatable in different directions at a certain angle, and a steeringtorque detector which is installed between the input shaft and theoutput shaft for thereby detecting a steering torque, a steering torquedetector of a steering system, comprising: left and right reflectionssurfaces formed in one of the input shaft and output shaft; a lightemitting element which is installed in a shaft corresponding to a shaftin which the reflection surface is formed; and left and right lightreceiving elements which are installed in left and right sides of thelight emitting element and receive light of the light emitting elementin accordance with a relative rotation of the input shaft and outputhaft.
 2. The detector of claim 1, wherein said left and right reflectionsurfaces are formed in the upper surfaces of left and right lightincident grooves formed in an end portion of an input shaft flangeintegrally formed in the input shaft, and the light emitting element andleft and right light receiving elements are installed an output shaftflange integrally formed in the output shaft in correspondence to theinput shaft flange.
 3. The detector of claim 2, wherein said left andright light incident grooves and left and right reflection surfaces areformed in such a manner that through hoes are formed in the input shaftflange, and a reflection plate is installed thereon.
 4. The detector ofclaim 2, wherein a protrusion is formed in one of the output shaftflange and the input shaft flange, and a guide groove is formed in othershaft flange corresponding to the shaft in which the protrusion isformed, and the protrusion is inserted into the guide grove for therebylimiting a relative rotation angle of the input shaft.
 5. The detectorof claim 1, wherein said light emitting element induces a resistancewhich is in reverse proportion to the intensity of incident light.